Global positioning system (GPS) navigational and position location systems are often used by military and civilian naval, ground, and airborne vehicles for navigation. GPS systems can experience blackout areas or regions when line-of-site (LOS) is broken with the satellites due to signal blockage. For example GPS systems often experience loss of signal when they are operated in dense urban environments next to large buildings (e.g., urban canyon).
Communications systems operating in the VHF/UHF and higher frequency bands have LOS problems similar to GPS. Vehicles operating in a city or in rugged or mountainous terrain have difficulty communicating due to signal link-loss and blockage. Furthermore, there are few technical options for delivering high-speed data, video, and position location information from a mobile unit or a large number of mobile units. For example, mobile units may include emergency response vehicles requiring broadband (last-mile) transmission of video from an emergency scene back to an emergency operations center. Rough terrain, line-of sight, ground network infrastructure and antenna technical challenges generally force or limit options having lower or unsatisfactory bit rate solutions.
LOS laser communications systems provide end-to-end or point-to-point systems where a laser transmitter must be pointed directly at a laser receiver to establish communications. As with some radio communications systems, these laser communications systems are not useable in rough terrain or urban canyon situations.